Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch sensor panels and touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location dictated by a user interface (UI) being displayed by the display device. In general, touch sensor panels and touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
Capacitive touch sensor panels can be formed from a matrix of drive and sense lines of a substantially transparent conductive material such as Indium Tin Oxide (ITO), often arranged in rows and columns in horizontal and vertical directions on a substantially transparent substrate. U.S. Pat. application Ser. No. 11/649,998 filed on Jan. 3, 2007 and entitled “Proximity and Multi-Touch Sensor Detection and Demodulation” (also incorporated by reference herein in its entirety) teaches a capacitive touch sensor array of uniform granularity capable of detecting multiple simultaneous touch events and a limited amount of proximity (or hover) events (near-field proximity sensing). In addition, that application discloses a proximity sensor array of fixed granularity capable of detecting multiple simultaneous proximity events (far-field proximity sensing). However, these fixed or uniform granularity proximity sensor arrays are incapable of being selectively configurable in real time to optimize their sensing capabilities, especially with regard to the detection of hovering objects whose distance to the touch sensor panel or touch screen may vary greatly.